To is used to begin a command procedure. You can think of to as a way to define a set of actions/verbs for NetLogo such as to go, to add-money, etc. You can use these verbs anywhere in the code. Note: You must put end at the end of the procedure in order for it to work. Procedures can also be called from buttons! For example, using a go button (which is located on the Interface tab) runs the procedure created as to go ... end. Let’s see that in action.

to setup
clear-all
create-turtles 100
end

Setup is the procedure name. Clear-all & create-turtles 100 are the commands in this procedure. And end tells NetLogo that the procedure is complete. When this is used as a button, this all happens at once.

Another purpose for this primitive is to divide code into smaller pieces. For example:

ask turtles [
  wiggle  ;; first turn a little bit
  move    ;; then step forward
]

to wiggle
  rt random 90
  lt random 90
end

to move
fd 1
end

See how in the first chunk of code, you are calling the turtles to wiggle, then move. Wiggle and move are then written as a command procedure. It ends up saving you a lot of space!